BQ24230H_14 Datasheet, PDF (22/38 Pages) Texas Instruments – USB-Friendly Lithium-Ion Battery Charger and Power-Path Management IC

bq24230H
bq24232H
SLUSBI8 – JANUARY 2014
www.ti.com
The allowed temperature range for a 103AT-2 type thermistor is 0°C to 50°C. However, the user can increase
the range by adding two external resistors. See Figure 24 for the circuit. The values for Rs and Rp are calculated
using the following equations:
-(R_TH + R_TC ) ±
æ
ççè (R_TH+R_TC
)²
-
4
ì
íî^RTH
´
R_TC + _(VH
V_H ´ V_C
- V_C ) ´
I_TS
´ (R_TC
üö
-
R_TH
)_ý
þ
÷÷ø
Rs =
2
(4)
( ) _{Rp =} V_H ´ R_TH + R_S
( ) I_TS ´ R_TH + R_S - V_H
(5)
Where:
R_TH: Thermistor Hot Trip Value found in thermistor data sheet
R_TC: Thermistor Cold Trip Value found in thermistor data sheet
V_H: IC's Hot Trip Threshold = 0.3V nominal
V_C: IC's Cold Trip Threshold = 2.1V nominal
I_TS: IC's Output Current Bias = 75µA nominal
NTC Thermsitor Semitec 103AT-4
Rs and Rp 1% values were chosen closest to calculated values
Cold Temp Resistance and
Trip Threshold; Ω (°C)
28000 (–0.6)
28480 (–1)
28480 (–1)
33890 (–5)
33890 (–5)
33890 (–5)
Hot Temp Resistance and Trip
Threshold; Ω (°C)
4000 (51)
3536 (55)
3021 (60)
4026 (51)
3536 (55)
3021 (60)
External Bias Resistor, Rs (Ω)
0
487
1000
76.8
576
1100
External Bias Resistor, Rp (Ω)
∞
845000
549000
158000
150000
140000
RHOT and RCOLD are the thermistor resistance at the desired hot and cold temperatures, respectively. Note
that the temperature window cannot be tightened more than using on the thermistor connected to TS, it can only
be extended.
bq2407x
I_NTC
TS
+
V_COLD
+ _VHOT
R_S
PACK+
TEMP
R_P
PACK-
Figure 24. Extended TS Temperature Thresholds
22
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